This invention relates generally to the field of storm water drainage systems, and in particular filtration of storm water run-off as captured, controlled and transported by storm water drainage systems. More particularly, the invention relates to the field of means to filter storm water or surface water run-off to remove hydrocarbons, organic liquids and other contaminants and particulate matter, as well to eradicate bacteria in the storm water run-off. Even more particularly, the invention relates to devices known as catch basin filters that are disposed in catch basins beneath storm water drain grates or curb inlets, typically found adjacent to paved roadways or parking lots.
As a result of society's high level of use of products containing hydrocarbons, organic liquids, phosphates, nitrates, heavy metals and other environmentally hazardous materials and chemicals, it is not uncommon for such components to be flushed in significant amounts into storm water drainage systems. It is therefore necessary to provide means and methods to remove such contaminants from the storm water prior to discharge of the storm water from the storm water system. In a common approach filtration means capable of capturing the contaminants are disposed at the ingress points of the storm water system, i.e., filter means are positioned in the storm drains such that the contaminants are immediately captured and storm water passing into the storm water drainage system is relatively contaminant-free. In another method, filtration means are positioned at the points of exit of the storm water system, such that the contaminants are removed prior to discharge into the environment. A typical storm drain comprises a surface opening covered by a grate, a curb inlet, or a combination of the two, where the surface opening leads directly into a catch basin, usually of a rectangular or cylindrical shape, that has a sump that allows particulates to settle. An outlet pipe connects to the catch basin above the sump and directs the storm water to a point of treatment or discharge.
Another problem inherent in storm water discharge is microbial contamination. Significant microbial contamination of discharge water results from the fact that storm water systems comprise vast networks of storm drains, conduits, collectors and the like, and all storm water run-off entering a storm water system does not immediately pass through the system. Instead there are large numbers of areas where the storm water remains resident in the system for extended periods of time. For example, the outlet pipes at the base of storm drains is typically connected to the catch basin several inches above the bottom of the basin to create a sump area to entrap sediments and other solid matter. This results in several inches of water that remaining trapped in the bottom or sump of each catch basin after a storm. This resident water is a prime breeding ground for bacteria, and over time the bacteria in the catch basin sumps multiply exponentially. When the next storm occurs the resident water in the catch basins is flushed and the bacterial concentration discharging from the storm system may exceed safe limits. In addition, the bacterial contamination of the resident sump water can result in odor problems.
Providing anti-microbial agents as a component of suspended filtration media at the ingress points of the storm system, i.e., the storm grates or curb inlets, such that the inflowing water contacts the anti-microbial agents does not solve this problem, as the amount of time that the bacteria is in contact with the anti-microbial agents in these pass-through catch basin filters is extremely short, and thus the effectiveness of the anti-microbial action is very limited if not completely ineffective. Because the anti-microbial agents are positioned above the sump area, they have no effect on bacterial growth in the resident water.
It is an object of this invention therefore, to provide a means for effectively reducing the bacterial concentration in storm water discharge. This is accomplished by providing a combination filtration and anti-microbial medium that, in addition to removing particulate matter from the storm water inflow, effectively reduces the concentration of bacteria in storm water that remains resident in sump areas at the bottom of a catch basin. The combination filtration and anti-microbial medium is at least partially disposed in the resident water at the bottom of the catch basin rather than being positioned merely as a pass-through filter, thereby increasing the contact time between the anti-microbial agents and the bacteria such that large amounts of bacteria are eradicated and explosive bacterial growth within the sump areas is precluded. It is a further object to increase the effective life of the filtration media by reducing the growth of bacteria, mold, algae and the like on the filtration media itself.